Studies of the nuclear processes of proton capture photon production and spallation neutron emission with advanced experimental techniques

Abstract: A series of nuclear reaction experiments have been performed in the intermediate energy range up to 1.6 GeV using advanced techniques to detect and measure neutral ejectiles resulting mainly from proton bombardment of both light and heavy nuclei.The proton Capture reaction A(p,γ)A+l was studied using a new type of pair spectrometer with large acceptance (PACMAN), which was designed and built for this purpose. The photons were converted to electron-positron pairs using a thin gold foil. Without this foil it was also possible to measure the A(p,e+e-)A+1 reaction. Complete γ-ray angular distributions for the radiative Capture of 98 MeV protons into 12C states were measured at the The Svedberg Laboratory (TSL) in Uppsala.Spallation neutron spectra for several targets and beam energies were measured at the Laboratoire National Saturne, Saclay using proton beams. To cover a large neutron energy range, two methods were employed; the high energy region (En > 200 MeV) was measured with a magnetic proton recoil spectrometer (MPR) using a liquid hydrogen converter, and the low energy region (En=2-400 MeV) with scintillators using the time-of-flight technique. The two methods are presented as well as the results on the doubly differential spallation cross sections of Pb(p,xn) at Ep=800, 1200 and 1600 MeV.A novel experiment on the neutron detection efficiency of a NE213 liquid scintillator in the energy range 20-100 MeV was performed at TSL. It was based on a high accuracy neutron tagging method in which 100 and 160 MeV neutrons were scattered off protons where the kinematics of the recoiling protons was fully determined. This provided the first spatially differential information on the detector response to neutrons, as well as the decomposition of the response on the charged particles involved and their energy. The instrumental work of this thesis also includes a discussion of the MPR technique over a large energy range (2 MeV to 1.6 GeV).

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